the present invention relates to a device and a method for the deboning of animal parts, in particular fowl parts.
The usual procedure for deboning animal parts is to strip the meat from the bone by forcing the bone in longitudinal direction through a small aperture in a meat stripper disc. The longitudinal movement of the bone through the aperture allows the meat to be scraped from the bone, along the length of the bone. Usually, the meat remains in a single mass after it has been stripped from the bone. An advantage of removing the bone from an edible poultry part is that the cooking time can be reduced. Also, the bone can be separately recovered and further processed for example as bone meal.
From the art, a plurality of methods and devices for removing the bones from the poultry parts are known.
From U.S. Pat. No. 4,893,378 a device is known wherein a plurality of deboning modules are mounted on a revolving support system. As the device revolves, poultry thighs are placed in sequence in the deboning modules and meat stripping is performed sequentially on each thigh. Each of the deboning modules includes a rotary bone holder for rotating the bone about its own longitudinal axis. Each of the deboning modules also includes a pair of notched stripping blades, which engage the bone and move along the length of the bone as the bone is rotated, to strip the meat from the bone. To enhance the meat removal, in the course of the stripping action a twisting action is imparted to the bone with respect to the meat.
The device disclosed in U.S. Pat. No. 4,893,378 however presents the disadvantage that, in order to allow the meat to be deboned, the meat needs to be cut from the bone before the deboning operation can be started. As the contours of the bone are mostly irregular and inflexible, the meat yield will be low. Also in order to allow the stripping blades to pass the knuckle in the course of the deboning operation, they will have to be opened and closed, which will further decrease the meat yield.
In U.S. Pat. No. 5,173,076 a device is disclosed which comprises a pair of spaced apart chain conveyors for carrying a plurality of deboning units mounted on the conveyors, along a substantially endless processing path. Each deboning unit comprises a carrier tray assembly for receiving the poultry parts that need be deboned, a bone pusher assembly mounted at one end of the carrier tray and a meat stripper disc assembly mounted at the opposite end of the carrier tray. The meat stripper disc assembly comprises a flexible meat stripper disc supported within a rigid collar. Approximately in the center of the meat stripper disc an aperture is provided for receiving the poultry bones there trough. Each bone pusher assembly comprises a hollow pusher sleeve with an open front end. The pusher sleeve is moveable in the direction of the meat stripper disc assembly. Within the pusher sleeve, a pusher rod is slideably mounted, which is moveable towards and throughout the aperture in the meat stripper disc.
In the course of a deboning operation, a poultry part is loaded into each carrier tray and moved towards the deboning position. As the carrier tray approaches the deboning position, the front end of the pusher sleeve engages the poultry part. As the open front end of the pusher sleeve contacts the meat stripper disc, the pusher rod is urged towards the meat stripper disc to engage the thigh bone and urge the thigh bone through the aperture of the meat stripper disc. To ensure that the bone is completely removed from the meat, the pusher rod is displaced to a position where it extends through the aperture of the meat stripper disc.
A problem that is often encountered with the type of system disclosed in U.S. Pat. No. 5,173,076 is that in the course the deboning process the bone is broken. As a consequence the broken parts need to be manually removed from the meat and the meat may contain bone fragments, which is unwanted. Also, the manual removal of bones from the poultry part is time consuming. There is thus a need to a machine that does not present the risk to damaging the bone in the course of the deboning operation.
It is the aim of the present invention to provide a deboning device with which the problem of bone breaking and bone fragmentation in the course of the deboning action can be overcome.
This is achieved by means of the technical features of the characterizing part of the first claim.
The device of the present invention is characterized by the presence of
a) clamping means for clamping at least part of the animal part within the deboning unit in longitudinal direction of the bone at a position between the bone pusher assembly and the meat stripper device,
b) means for supporting the meat in cross direction of the bone in the course of the deboning action, whereby around the meat sufficient free space is left to allow the meat to be compressed
c) means for retaining the bone after it has been displaced through the aperture of the meat stripper disc.
An analysis of the problem encountered with the device known from the state of the art has revealed that in the course of the deboning action, the bone pusher assembly first engages the top of the bone after which at least part of the bone pusher assembly is displaced within the animal part through the hole created in the animal part by the leaving bone, towards the meat stripper disc. In that way the bone is forced to leave the animal part in longitudinal direction thereof, towards and through the aperture in the meat stripper disc.
An analysis of the problem encountered with the device known from the state of the art has also revealed that as the bone pusher assembly is advanced through the interior of the animal part during the deboning process, the meat is compressed in longitudinal direction of the bone. In case of rather large animal parts with a large volume of meat, substantive power is required to force the bone to leave the meat and to displace the bone through the meat stripper disc. In the known device where the meat is carried in a carrier tray, often insufficient space is left to allow the meat to expand sufficiently in cross direction of the part. As a consequence, breach of the bone is a problem that is often encountered with. By providing in the device of this invention space to allow the meat to expand in cross direction of the animal part, bone cracking can be avoided. By providing in the device of this invention space to allow the meat to expand also the risk that the animal part is projected out of the deboning unit, because the resistance exerted by the aperture of the meat stripper disc is too large, can be minimized. The clamping force exerted to the bone allows ensuring a proper positioning of the animal part with respect to the meat stripper disc.
The means for retaining the bone after it has been displaced through the aperture of the meat stripper disc allow preventing a turning over of the bone in the advancing direction of the device at a too early stage, after the bone has been displaced out of the meat. A turning over of the bone at a too early stage could involve a blocking of the device and the need to manually remove the animal part from the device and to complete the deboning in a manual manner.
In a first preferred embodiment of this invention, at least part of the bone pusher assembly is displaceable through the aperture in the meat stripper device, to a position where it extends from the aperture of the meat stripper disc over a distance of approximately 1-1000 mm beyond the meat stripper disc. The distance over which the bone pusher assembly extends beyond the meat stripper disc is preferably equal to or larger than the length of the tendons. In that way a complete separation of meat and bone can be ensured even in case of parts wherein a strong bonding of the tendons to the bone is present. Such strong bonding can for example be found in larger animal parts for example turkey drums.
Preferably, in the deboning unit of the device of this invention means are provided for adjusting the positioning of the clamping means to the length of the animal part, so as to allow the device to be used for the deboning of animal parts of varying sizes. Thereto, the bone pusher assembly preferably comprises a pusher rod, which is slideably moveable within the deboning unit towards a retracted position so as to allow the animal part to be inserted, and from the retracted position towards an extended position in the course of the deboning operation. The clamping force is then exerted by the weight of the bone pusher assembly. The meat stripper disc preferably supports the animal part.
The pusher rod preferably comprises at a side facing the meat stripper device a head part that is shaped to engage a first end of the bone. In that way an appropriate clamping force can be exerted to the bone and it is ensured that the deboning operation proceeds as complete as possible. Thereby the shape of the head part is adapted, for example complementary to the shape of the bone to be received by it. The head part may comprise one or more longitudinally extending pins for engaging the cartilage and/or upper part of the bone. Preferably also, the surface of the head part is roughened and is provided with a coating of an elastic material so as to prevent damaging of the bone and to minimize the amount of bone fragments splitting from the bone in the course of the deboning operation.
The head part may either by fixed to the pusher rod, or be removably mounted. In the latter case the head part used may be adapted to the nature of the animal parts that need deboning.
In order to allow an improved deboning of large animal parts, it is important that the aperture in the meat stripper disc remains aligned with the bone pusher assembly, and that the meat stripper disc remains in the position as it was mounted within the meat stripper device. Also the meat stripper disc should be capable of withstanding large traction forces when the bone is forced through the aperture in the meat stripper disc. To solve this problem, the meat stripper device comprises at a side pointing away from the bone pusher assembly, a frame for receiving and supporting the meat stripper disc along at least part of its circumference. Preferably, at a side facing the bone pusher assembly, clamping means are provided for removably clamping the meat stripper disc within the frame.
Preferably the meat stripper disc comprises a circumferential rim which surrounds an internal part comprising the aperture. The thickness of the circumferential rim is less than the material thickness of the internal part of the meat stripper disc. Preferably also the material thickness of the internal part of the meat stripper disc decreases towards the aperture. This can for example be achieved by means of a meat stripper disc of which the side facing the part to be deboned is concave. The concave shape provides an improved guiding of the bone towards the aperture, as a consequence of which bone breaching can be minimized and the yield of the amount of meat retained after the deboning operation can be increased.
An improved bending of the meat stripper disc is especially of importance in case the diameter of the aperture in the meat stripper disc is chosen to be smaller than the smallest diameter of the bone. A small diameter of the aperture is mostly chosen so as to improve the deboning operation and to allow as much meat to be recovered as possible. In that case however substantive forces are needed to force the bone to move through the aperture in the meat stripper disc.
The bone pusher assembly of the device of this invention, preferably also comprises a central tube in which the pusher rod is fixed, the central tube being slideably moveable within a cylinder simultaneously with the pusher rod. Preferably also means are provided to avoid that the pusher rod can rotate with respect to the bone and the bone is broken or projected out of the deboning unit.
Furthermore, at a position beyond the meat stripper disc and aligned with the aperture of the meat stripper disc, in the deboning unit means are provided for receiving and retaining the bone in longitudinal direction, after it has been displaced through the aperture meat stripper disc.